Circulating systems are known in which the cooled down water content of the hot water circulation line is conveyed back into the hot water tank via a recirculation pipe as disclosed in our earlier U.S. Pat. No. 5,143,049. Subsequent retrofit of a recirculation system requires additional piping which may be difficult to install. A different ferent hot water recovery system is disclosed in U.S. Pat. No. 5,009,572 Imhoff et al. and U.S. Pat. No. 5,277,219 Lund, in which a pump 46 has to be switched on if the hot water temperature near the faucet drops below a pre-determined level or is switched on as soon as a hot water faucet is opened. To economize the hot water usage the pump 46 conveys the cooled-down content of the hot water line back through the cold water line into the water heater. Thus the faucets in the distribution line receive warm water when the cooled-down water content between the water heater and the faucets has been pumped into the cold water line.
The aforesaid U.S. Pat. Nos. 5,009,572 Imhoff et al.; 5,143,049 Laing et al.; and 5,277,219 Lund are incorporated into this specification by this reference.
The prior art systems that recirculate the cooled-down portion of the hot water line directly through the cold water line have several drawbacks. The most serious is the fact that the cold water line is first filled with luke warm water. If cold water is needed right after a recirculation cycle, the user must wait several seconds for the heated water to be purged from the cold water line. Another drawback results from the fact that the warm water stream may build up scaling in the cold water line.
The present invention avoids these drawbacks.